Spatial-frequency selection using downconversion optical parametric amplification

We have observed spatial-frequency selection using downconversion optical parametric amplification in lithium iodate. A mode-locked Nd:YAG laser with a second harmonic generator provided the pump beam at 532 nm and the signal beam at 1064 nm. An image was placed on the signal beam and spatial frequencies from 0 to 60 lines/mm were selectively amplified from the image by rotating the lithium iodate crystal 0°–0.77° from the phase-match angle. The optical parametric amplifier’s passband behavior was in excellent agreement with the existing theory.